Human papillomavirus (HPV) is a circular, non-enveloped dsDNA virus that infects squamous epithelial cells. HPV enters the body, usually through a break in the skin, and then infects the cells in the layers of the skin. HPV is transmitted by skin-to-skin contact. HPV infections can be acquired through a cut or through sexual activity with an infected person. This includes kissing or touching the skin of the infected areas and having intercourse. A mother with a genital HPV infection may also transmit the virus to the infant during labour.
HPVs are a group of more than 120 related viruses, 33% of which are known to infect genital tract (Microbiology and Molecular Biology Reviews, 2004, 68 (2):362-372). Certain types of human papillomavirus are able to transform normal cells into abnormal ones which can go on to form cancer. Accordingly, these viruses are classified as high-risk types and low-risk types. High-risk HPVs are associated with cancers. Genital HPV infections are very common and can lead to anogenital cancers. Persistent infections with high-risk HPVs are the primary cause of cervical cancer. HPV infections also cause anal cancer, vulvar cancer, vaginal cancer and penile cancer (Int. J. Cancer, 2006, 118(12): 3030-44). The high risk subtypes are HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68, the most common being HPV 16, 18, 31, 33 and 45. Further, several types of HPVs, particularly type 16, have been found to be associated with HPV-positive oropharyngeal cancer, a form of head and neck cancer (N. Engl. J. Med., 2007, 356(19):1944-56).
High risk HPVs produce two oncoproteins, E6 and E7, which are necessary for viral replication. During the HPV infection in humans, the HPV E6 protein binds and promotes the degradation of tumor suppressor p53 by an ubiquitin-mediated pathway diminishing the ability of the cell to undergo apoptosis. The HPV E7 protein binds and degrades the retinoblastoma protein (pRb), preventing it from inhibiting the transcription factor E2F, resulting in loss of cell cycle control.
It has been estimated that HPV accounts for approximately 5% of all cancers worldwide (Int. J. Cancer, 2006, 118(12):3030-3044).
Cancer of the cervix uteri is the second most common cancer among women worldwide. About 86% of the cases occur in developing countries. Cervical cancer accounts to 13% of the cancers occurring in females (World: Human Pappilomavirus and related cancers, summary report, November 2010).
Persistent Human papillomavirus (HPV) infections are now recognized as the cause of essentially all cervical cancers. According to the American Cancer Society, in 2010, about 12,000 women in the United States would be diagnosed with this type of cancer and more than 4,000 would die from it. Cervical cancer is diagnosed in nearly half a million women each year worldwide, claiming a quarter of a million lives annually.
Vulvar and Vaginal cancers account to about 3 to 5% and 1-2% respectively of all gynecologic cancers and penile cancers accounts to about 0.2% of all cancers in the United States. Despite their infrequency, vulvar, vaginal and penile cancers remain important diseases, because of their significant impact on sexuality. Though there is no single etiologic factor, there is a strong association with HPV infection. HPV is thought to be responsible for about 40% of penile cancers. Many studies have shown the presence of HPV types 16 and 18 in penile carcinoma (Hum. Pathol., 1991, 22:908-913). HPV is also responsible for about 65% of vaginal (International Journal of Cancer, 2009, 124(7):1626-1636) and 50% of vulvar cancers (Vaccine, 2006, 24 (suppl 3): S11-S25) and HPV-16 accounted for most HPV positive cases for both the cancers (Obstet. Gynecol., 2009, 113(4):917-24).
HPV infection is also associated with anal cancer. It is estimated that about 1,600 new cases of HPV associated anal cancers are diagnosed in women and about 900 are diagnosed in men each year in the United States. In general, HPV is thought to be responsible for about 90% of anal cancers (International Journal of Cancer, 2009, 124(7):1626-1636). Notably HPV 16 seems to be responsible for most of the anal cancer. According to a study HPV 16, was detected in 84 percent of anal cancer specimens examined (New England Journal of Medicine, 1997, 337(19)1350-8).
Cancer of head and neck typically refers to squamous cell carcinomas of the head and neck. Head and neck cancers account for approximately 3 percent of all cancers in the United States (A Cancer Journal for Clinicians, 2010, 60(5): 277-300). Head and neck cancers are identified by the area in which they begin. They are typically classified as: cancers of oral cavity, salivary gland, paranasal sinuses, nasal cavity, pharynx, nasopharynx, oropharynx, hypopharynx, larynx and lymph nodes in the upper part of the neck. Cancer of the oral cavity (the front two-thirds of the tongue, the gingiva, the buccal mucosa, the floor of the mouth under the tongue, the hard palate, and the small area behind the wisdom teeth) and cancer of the oropharynx (the soft palate, the base of the tongue, and the tonsils) are the most common types of cancer caused by HPV. Studies have shown that about 60% of oropharyngeal cancers are caused by HPV (Cancer Epidemiology, Biomarkers and Prevention, 2005, 14(2):467-475), in particular HPV16, is a causal factor for some head and neck squamous cell carcinoma (HNSCC).
HPV has also been associated with lung carcinomas. According to the published articles the incidence of HPV in lung cancer was 24.5% (Lung Cancer, 2009, 65: 13-18). A study conducted in China revealed that the risk of lung squamous cell carcinomas was 3.5 times higher among HPV-positive population compared with the HPV-negative population and 16.9 times higher for patients with positive HPV-16 than negative HPV-16 (Oncol. Rep., 2009, 21(6)1627-32).
A role for human papillomaviruses has also been proposed in a diverse range of other malignancies, particularly, non-melanoma skin cancer the commonest malignancy in fair-skinned populations worldwide. Skin cancer is rarely fatal and is responsible for less than 1% of all cancer deaths. However its impact on the public health is nevertheless considerable. The involvement of HPV in human skin cancer was first demonstrated in patients with the rare hereditary disease epidermodysplasia verruciformis (Journal of National Cancer Institute Monographs, 2003, No. 31).
HPV is also associated with intraepithelial neoplasia of the conjunctiva (0-80%) and in 62-100% of invasive carcinomas of the conjunctiva, eyelid and lacrimal sac (IARC Monographs, 64:130). There is a strong association between HPV and conjunctival papillomas. HPV type 6/11 is the most common HPV type in conjunctival papilloma (Br. J. Opthalmol., 2001, 85:785-787).
HPV 6, 11 and 13 are typically labeled as low-risk, because the infection with these types has low oncogenic potential and usually results in the formation of benign lesions such as genital warts (technically known as condylomata acuminata) and mild dysplasia of the cervix, HPV 6 and 11 are also associated with conjunctival papilloma.
Despite the high incidence of genital HPV infection and its association with malignant diseases, there is no effective antiviral therapy for HPV infection. Gardasil® and Cervarix® are the two vaccines currently on the market against two of the most common high risk HPVs (HPV 16 and 18). However, they are only of prophylactic type and do not treat the existing HPV associated cancer. Moreover, the high cost, issues with social acceptance, and limitations in health care systems through which the vaccine can be provided, limits the availability of this vaccine to women, particularly in developing countries where HPV-associated anogenital cancers (relating to the anus and the genitals) are most commonly found. Consequently there remains a need to identify other, less expensive and more universally available approaches for preventing and/or treating HPV associated cancers.
The inventors have surprisingly found that pyrrolidine substituted with flavone derivatives are effective against cancers associated with HPV.
The invention described herein provides pyrrolidine substituted with flavone derivatives represented by Formula (I) (as described herein) for the treatment of human papilomavirus associated cancers.